Disclosed in the embodiments herein is an improved system for sheet lateral position registration (sheet rotational position registration) for print media sheets, especially for an improved xe2x80x9cTELERxe2x80x9d type of combined lateral sheet registration and deskewing system for a printer.
More specifically, there is disclosed in the embodiments herein an improved integral sheet registration system, especially suited for high speed printers, for providing both sheet deskewing and lateral sheet registration, which provides increased re-centering time, and thus increased acceleration and deceleration latitudes, for the lateral translation movement of the lateral sheet registration system. In the disclosed embodiments this is provided by varying radius sheet feeding rollers providing lateral registration by side-shifting, but with automatic nip openings in their rotations. Additionally disclosed are specially positioned non-slip sheet feeding nips positioned in the paper path between said varying radius rollers and the image transfer station of the printer.
Various sheet registration systems are known in the art, and the present system is not limited to any particular such registration, deskew and/or side-shifting system. Various TELER systems of sheet registration have differential roll pair driving for deskew and sheet side-shifting systems in which the entire structure and mass of the carriage containing the two drive rollers, their opposing nip idlers, and their drive motors connected), is axially side-shifted to side-shift the engaged sheet into lateral registration. These may be referred to as xe2x80x9cTELERxe2x80x9d systems, of, e.g., U.S. Pat. No. 5,094,442, issued Mar. 10, 1992 to Kamprath et al; U.S. Pat. Nos. 5,794,176 and 5,848,344 to Milillo et al; U.S. Pat. No. 5,219,159, issued Jun. 15, 1993 to Malachowski and Kluger (citing numerous other patents); U.S. Pat. No. 5,337,133; and other cited patents.
Additional background of interest includes a Xerox Corp. U.S. Pat. No. 5,278,624, issued Jan. 11, 1994 to David R. Kamprath and Martin E. Hoover, showing another example of a xe2x80x9cTELERxe2x80x9d type of combined lateral sheet registration and deskewing system for a printer with a single drive motor and reduced mass of the xe2x80x9cTELERxe2x80x9d lateral translation (side shifting) components. Reduced mass is helpful to allow the re-centering or return to a xe2x80x9chomexe2x80x9d position of TELER systems in the very short time and space available between successive sheets in the sheet path of a high speed printer. That is because sheet lateral (side-shift) registration is accomplished in a TELER system by side-shifting the TELER sheet drive rolls and their associated components while the sheet is engaged in the feed nip of those TELER sheet drive rolls.
Also of particular background interest is a Xerox Corp. U.S. Pat. No. 5,078,384 issued Jan. 7, 1992 to Steven R. Moore. This is not a TELER system. Rather, it accomplishes sheet deskewing and downstream or forward direction registration by differential driving of two sheet drive rolls 24, 25, by two servomotors, but does not provide sheet lateral (sideways) registration by any side-shifting of those drive rolls. Thus, it does not teach or suggest (or even have the problem of) accomplishing rapid re-centering of a TELER system in between operative sheet nip engagements. However, this U.S. Pat. No. 5,078,384 does show the use of xe2x80x9cDxe2x80x9d shaped (partially relieved radius) drive rolls 24,25 to disengage those drive rolls from the sheet (opening the drive nip) when those drive rolls are rotated to the position in which the reduced radius xe2x80x9cflatxe2x80x9d portion of those xe2x80x9cDxe2x80x9d shaped drive rolls is facing the sheet and becomes spaced therefrom due it the reduced radius of that portion of the roll.
xe2x80x9cDxe2x80x9d shaped sheet feeding rolls are, of course, used in various other paper sheet feeding applications. For example, Xerox Corp. U.S. Pat. No. 5,449,165, issued Sep. 12, 1995, discloses a 90 degree paper feed transition module with transversely mounted and intermittently rotated xe2x80x9cDxe2x80x9d shaped feed rolls. Xerox Corp. U.S. Pat. No. 4,929,128, issued May 22, 1990 to Stemmle, shows typical segmented or xe2x80x9cDxe2x80x9d shaped feed rolls for initial sheet feeding, and for duplex path sheet feeding. However, the present embodiment provides normal and even closed nip sheet nip engagement and feeding, unlike such xe2x80x9cDxe2x80x9d roller sheet feed systems in which a stationary sheet is unevenly accelerated by initial engagement of a xe2x80x9ccornerxe2x80x9d of the xe2x80x9cDxe2x80x9d roller (where the xe2x80x9cDxe2x80x9d roller transitions from it""s smaller to it""s larger radius) with the sheet.
There is a further, often unappreciated, problem in TELER systems, of particular interest here. A sheet which has just been accurately deskewed and laterally (side) registered by a TELER system cannot be released from the TELER nips until after that same sheet is firmly acquired by a downstream sheet transport in the paper path (normally a transfer station) which will prevent that sheet from losing the lateral registration and deskewed rotational orientation registration just given to that sheet by the TELER system. Thus, the timing of the release of the TELER nips is critically related not only to the time available and needed for re-centering before the next sheet is acquired (as noted above) but also to the timing of the acquisition of the sheet by the next downstream sheet transporting system.
Thus, in the disclosed embodiment, non-slip downstream sheet acquisition nips are specially positioned in relation to the TELER system feed rolls. In particular, in the disclosed embodiment, plural laterally spaced sheet positional stabilization roller nips are positioned downstream from the nips of xe2x80x9cDxe2x80x9d shaped TELER rollers (having a sheet engaging peripheral circumference area and a non-sheet engaging peripheral circumference area) by a distance downstream which is less than the circumference of the sheet engaging peripheral circumference area, to insure that the sheet will not be released from the sheet lateral and rotational registration position just provided by the TELER system. In the disclosed embodiment those plural laterally sheet positional stabilization roller nips are positioned in the paper path in between the TELER roller nips and the image transfer station of the printer, for further insuring of the maintenance of the side registration and deskewing of that sheet as that sheet is fed into the image transfer station. That is, in this embodiment the sheet is not released from its stabilizing nips until after at least a substantial portion of that sheet is fully acquired by the image transfer station. By xe2x80x9cfully acquiredxe2x80x9d it is meant that a sufficiently substantial area of that sheet has been electrostatically tacked to the photoreceptor by transfer corona electrostatic charges (or acquired by a biased transfer roller nip with the photoreceptor) for further, non-slip, movement of that sheet by and with the moving photoreceptor, as will be well understood in the xerographic arts.
Various other prior automatic sheet lateral registration and deskewing systems are known in the art. The below-cited patent disclosures are noted by way of some further examples. They demonstrate the long-standing efforts in this technology for more effective yet lower cost sheet lateral registration and deskewing, particularly for printers (including, but not limited to, xerographic copiers and printers). They demonstrate that it has been known for some time to be desirable to have a sheet deskewing system that can be combined with a lateral sheet registration system, in a sheet driving system also maintaining the sheet forward speed and registration (for full three axis sheet position control) in the same apparatus. That is, it is desirable for both the sheet deskewing and lateral registration to be done while the sheets are kept moving along a paper path at a defined substantially constant speed. Otherwise known as sheet registration xe2x80x9con the flyxe2x80x9d without sheet stoppages.
Yet these various prior systems have had some difficulties, which the novel system disclosed herein addresses, as further shown and described below. Especially, for the faster sheet feeding rates and decreased miss-registration tolerances of quality high speed printing systems.
For faster printing rates, requiring faster sheet feeding rates along paper paths, which can reach more than, for example, 100-200 pages per minute, the above combined systems and functions become much more difficult and expensive. Especially, to accomplish the desired sheet skew rotation, sheet lateral movement, and forward sheet speed during the brief time period in which each sheet is in the sheet driving nips of the combined system. As further discussed below, such high speed sheet feeding for printing or other position-critical applications heretofore has commonly required, for the lateral sheet registration, rapid acceleration and deceleration lateral (sideways to the sheet path) movements of relatively high mass system components, and substantial power for that rapid acceleration and rapid movement. Or, rapid xe2x80x9cwigglingxe2x80x9d of the sheet by deskewing, deliberately skewing, and again deskewing the sheet for side registration, during that same brief time period the sheet is held in the sheet feeding nips of the system. However, the sheet handling system disclosed herein is not limited to only high speed printing applications.
Disclosed in the embodiment herein is an improved system for controlling, correcting or changing the orientation and position of sheets traveling in a sheet transport path. In particular, but not limited thereto, sheets being printed in a reproduction apparatus, which may include sheets being fed to be printed, sheets being recirculated for second side (duplex) printing, and/or sheets being outputted to a stacker, finisher or other output or module.
The disclosed embodiment can provide in the same unit both active automatic variable sheet deskewing and active variable side shifting for lateral registration while the sheet is moving uninterruptedly at process speed. It is applicable to various reproduction systems, generally referred to herein as printers, including high-speed printers, and other sheet feeding applications.
Various other types of lateral registration and deskew systems are known in the art. A recent example is Xerox Corp. U.S. Pat. No. 6,173,952 B1, issued Jan. 16, 2001 to Paul N. Richards, et al (and art cited therein). That patents disclosed additional feature of variable lateral sheet feeding nip spacing, for better control over variable size sheets, may be readily combined with or into various applications of the present invention, if desired.
As noted, it is particularly desirable to be able to do lateral registration and deskew xe2x80x9con the fly,xe2x80x9d while the sheet is moving through or out of the reproduction system at normal process (sheet transport) speed. Also, to be able to do so with a system that does not substantially increase the overall sheet path length, or increase paper jam tendencies. The following additional patent disclosures, and other patents cited therein, are noted by way of some examples of sheet lateral registration systems with various means for side-shifting or laterally repositioning the sheet: Xerox Corp. U.S. Pat. No. 5,794,176, issued Aug. 11, 1998 to W. Milillo; U.S. Pat. No. 5,678,159, issued Oct. 14, 1997 to Lloyd A. Williams et al; U.S. Pat. No. 4,971,304, issued Nov. 20, 1990 to Lofthus; U.S. Pat. No. 5,156,391, issued Oct. 20, 1992 to G. Roller; U.S. Pat. No. 5,078,384, issued Jan. 7, 1992 to S. Moore; U.S. Pat. No. 5,094,442, issued Mar. 10, 1992 to D. Kamprath et al; U.S. Pat. No. 5,219,159, issued Jun. 15, 1993 to M. Malachowski et al; U.S. Pat. No. 5,169,140, issued Dec. 8, 1992 to S. Wenthe; and U.S. Pat. No. 5,697,608, issued Dec. 16, 1997 to V. Castelli et al. Also, IBM U.S. Pat. No. 4,511,242, issued Apr. 16, 1985 to Ashbee et al.
Various optical sheet lead edge and sheet side edge position detector sensors are known which may be utilized in such automatic sheet deskew and lateral registration systems. Various of these are disclosed the above-cited references and other references cited therein, or otherwise, such as the above-cited U.S. Pat. No. 5,678,159, issued Oct. 14, 1997 to Lloyd A. Williams et al; and U.S. Pat. No. 5,697,608 to V. Castelli et al.
Various of the above-cited and other patents show that it is well known to provide integral sheet deskewing and lateral registration systems in which a sheet is deskewed while moving through two laterally spaced apart sheet feed roller-idler nips, where the two separate sheet feed rollers are independently driven. Temporarily driving the two nips at slightly different rotational speeds provides a slight difference in the total rotation or relative pitch position of each feed roller while the sheet is held in the two nips. That moves one side of the sheet ahead of the other to induce a skew (small partial rotation) in the sheet opposite from an initially detected sheet skew in the sheet as the sheet enters the deskewing system. Thereby deskewing the sheet so that the sheet is now oriented with (in line with) the paper path.
For printing in general, the providing of both sheet skewing rotation and sheet side shifting while the sheet is being fed forward in the printer sheet path is a technical challenge, especially as the sheet path feeding speed increases. Print sheets are typically flimsy paper or plastic imageable substrates of varying thinness"", stiffness"", frictions, surface coatings, sizes, masses and humidity conditions. Various of such print sheets are particularly susceptible to feeder slippage, wrinkling, or tearing when subject to excessive accelerations, decelerations, drag forces, path bending, etc.
The above-cited Xerox Corp. U.S. Pat. No. 4,971,304, issued Nov. 20, 1990 to Lofthus (and various subsequent patents citing that patent, including the above-cited Xerox Corp. U.S. Pat. No. 6,173,952 B1, issued Jan. 16, 2001 to Paul N. Richards et al) are of interest as showing that a two nips differentially driven sheet deskewing system, as described above, can also provide sheet lateral registration in the same unit and system, by differentially driving the two nips to provide full three axis sheet registration with the same two drive rollers, plus appropriate sensors and software. That type of deskewing system can provide sheet lateral registration by deskewing (differentially driving the two nips to remove any sensed initial sheet skew) and then deliberately inducing a fixed amount of sheet skew (rotation) with further differential driving, and driving the sheet forward while so skewed, thereby feeding the sheet sideways as well as forwardly, and then removing that induced skew after providing the desired amount of sheet side-shift providing the desired lateral registration position of the sheet edge. This Lofthus-type system of integral lateral registration does not require rapid side-shifting of the mass of the sheet feed nips and their drives, etc., for lateral registration like a TELER type system. However, as noted, this Lofthus-type of lateral registration requires rapid plural rotations (high speed xe2x80x9cwigglingxe2x80x9d) of the sheet. That has other challenges with increases in the speed of the sheet being both deskewed and side registered by plural differential rotations of the two nips, requiring additional controlled differential roll pair driving, especially for large or heavy sheets.
In contrast to the above-described Lofthus ""304 type system of sheet lateral registration are prior TELER type sheet side-shifting systems, in which the entire structure and mass of the carriage containing the two drive rollers, their opposing nip idlers, and the drive motor(s) (unless, e.g., the drive motor(s) are splined drive telescopically connected), is axially side-shifted to side-shift the engaged sheet into lateral registration. In the latter systems the sheet lateral registration movement can be done during the same time as, but independently of, the sheet deskewing movement, thereby reducing the above-described sheet rotation requirements. These may be broadly referred to as xe2x80x9cTELERxe2x80x9d systems, of, e.g., U.S. Pat. No. 5,094,442, issued Mar. 10, 1992 to Kamprath et al; U.S. Pat. Nos. 5,794,176 and 5,848,344 to Milillo et al; U.S. Pat. No. 5,219,159, issued Jun. 15, 1993 to Malachowski and Kluger (citing numerous other patents); U.S. Pat. No. 5,337,133; and other above-cited TELER patents and applications.
For high speed sheet feeding, however, a rapid lateral acceleration and deceleration of a substantial mass in such prior TELER systems requires yet another fairly large drive motor to accomplish the side shift in the brief time period in which the sheet is still held in (but passing rapidly through) the pair of drive nips and then rapidly re-center that mechanism by a reverse side-shift movement in the typically very much briefer time period available before the next sheet reaches the two nips of the TELER system. That is, the entire deskew mechanism of two independently driven transversely spaced feed roll nips and their mounting carriage must move laterally by a variable distance each time an incoming sheet is optically detected as needing lateral registration, by the amount of side-shift needed to bring that sheet into lateral registration. Then the entire TELER side-shifting system must return even faster, re-centering after each sheet or after a series of sheets have required a series of side shifts in the same direction by a predetermined excessive total distance. That is, an even more rapid opposite transverse return movement of the same large mass is required in prior TELER systems in order to return the system back to its xe2x80x9chomexe2x80x9d or centered position before the (closely following) next sheet enters the two drive nips of the system.
Especially if each sheet is entering the system laterally miss-registered in the same direction, as can easily occur, for example, if the input sheet stack side guides are not in accurate lateral alignment with the machines intended alignment path, which is typically determined by the image position of the image to be subsequently transferred to the sheets.
In any of these systems, the use of sheet position sensors, such as a CCD multi-element linear strip array sensor, may be used in a feedback loop for slip compensation to insure the sheet achieving the desired three-axis registration. See, e.g., the above-cited U.S. Pat. No. 5,678,159 to Lloyd A. Williams, et al.
Also, the disclosed embodiment does not require pivoting nips, which have other issues, and allows the use of otherwise normal low slippage high friction feed rollers which may provide normal roller-width sheet engagement in the sheet feeding nips with an opposing idler roller.
Although the drive systems illustrated in the example herein are shown in a direct drive configuration, that is not required. For example, a timing belt or gear drive with a drive ratio could be alternatively used.
A specific feature of the specific embodiment disclosed herein is to provide a sheet lateral registration system for sequentially laterally registering and feeding sheets moving in a sheet path direction, comprising at least two spaced apart sheet feeding rollers providing defined intermittent sheet engagement and sheet disengagement nips, a rotatable drive system for said at least two spaced apart sheet feeding rollers, a lateral shifting system for laterally moving a sheet by laterally shifting said at least two spaced apart sheet feeding rollers laterally relative to said sheet path direction while a sheet is engaged in said intermittent sheet engagement nips of said at least two sheet feeding rollers, and said lateral shifting system having a home position and intermittently laterally shifting said at least two spaced apart sheet feeding rollers towards said home position of said lateral shifting system without laterally moving said sheet while a sheet is in said intermittent sheet disengaged nips of said at least two sheet feeding rollers.
Further specific features disclosed in the embodiment herein, individually or in combination, include those wherein said at least two spaced apart sheet feeding rollers provide said defined intermittent sheet engagement and sheet disengagement nips by said at least two sheet feeding rollers having at least two different radii in at least two different circumferential areas which alternately engage and disengage the sheet as said at least two sheet feeding rollers are rotated by said rotatable drive system to provide increased time for said laterally shifting of said at least two sheet feeding rollers towards said home position of said lateral shifting system by disengaging from a sheet substantially before the sheet leaves said sheet lateral registration system, and/or wherein opposing idlers are mounted for lateral movement together with said at least two spaced apart sheet feeding rollers, and said two spaced apart sheet feeding rollers have similar major larger radius cylindrical circumferential lengths and minor smaller radius non-cylindrical circumferential lengths respectively automatically providing with said rotation thereof closed nip sheet feeding and open nip sheet release relative to said opposing idlers, and/or wherein said larger radius circumferential lengths of said at least two spaced apart sheet feeding rollers are coordinated to the downstream distance to a subsequent sheet acquisition system, and/or wherein said sheet lateral registration system is integral a high speed printer with an image transfer station in said sheet path, said high speed printer having a subsequent sheet acquisition system comprising non-slip sheet feeding nips positioned in said sheet path between said sheet lateral registration system and said image transfer station of said high speed printer, and/or wherein said at least two spaced apart sheet feeding rollers provide sheet deskewing by differential rotation as well as said lateral sheet registration, and/or wherein said sheet lateral registration system is integral a high speed printer sheet path having closely sequentially spaced print media sheets moving at high speed therein, and said sheet lateral registration system provides lateral registration of said print media sheets, and/or wherein said at least two spaced apart sheet feeding rollers have opposing idlers, said at least two spaced apart sheet feeding rollers provide said defined intermittent sheet engagement and sheet disengagement nips by said at least two sheet feeding rollers having at least first and second different radii in at least first and second different circumferential areas which respectively alternately engage and disengage opposing idlers to provide respective opened and closed sheet feeding nips as said at least two sheet feeding rollers are rotated by said rotatable drive system, said opened sheet feeding nips provide said increased time for said laterally shifting of said at least two sheet feeding rollers towards said home position of said lateral shifting system by disengaging from a sheet substantially before the sheet leaves said sheet lateral registration system, and said defined intermittent sheet engagement nips are automatically closed before a sheet is received therein, and/or a sheet lateral registration system for sequentially laterally registering and feeding sheets moving in a sheet path direction with at least two laterally spaced apart sheet feeding and registration rollers forming sheet feeding nips with opposing idlers, said at least two laterally spaced apart sheet feeding and registration rollers are laterally moveable relative to said sheet path direction towards and away from a lateral home position, said at least two laterally spaced apart sheet feeding and registration rollers have at least first and second different circumferential surface areas, respectively, having a larger radius and a smaller radius, a roller rotational drive system selectively intermittently partially rotates said at least two sheet feeding and registration rollers to intermittently form a closed sheet feeding nip with said first and larger radius circumferential surface areas with said idlers, said roller rotational drive system selectively intermittently further partially rotating said at least two sheet feeding and registration rollers to intermittently form an open non sheet feeding gap from said idlers with said second and smaller radius of said second circumferential surface areas, a lateral movement system for intermittently laterally shifting said at least two spaced apart sheet feeding rollers laterally relative to said sheet path direction while a sheet is engaged in said closed sheet feeding nip of said at least two sheet feeding rollers for laterally registering the sheet, and said lateral movement systems intermittently laterally shifting said at least two spaced apart sheet feeding rollers towards said home position thereof without laterally moving a sheet while a sheet is in said intermittent sheet disengaged nips of said at least two sheet feeding rollers to provide increased time for said laterally shifting of said at least two sheet feeding rollers towards said home position, and/or a sheet lateral registration method for sequentially laterally registering and feeding sheets moving in a sheet path direction with at least two laterally spaced apart sheet feeding and registration rollers forming sheet feeding nips with opposing idlers, said at least two laterally spaced apart sheet feeding and registration rollers being laterally moveable relative to said sheet path direction towards and away from a lateral home position, said at least two laterally spaced apart sheet feeding and registration rollers having at least first and second different circumferential surface areas respectively having a larger radius and a smaller radius, selectively intermittently partially rotating said at least two sheet feeding and registration rollers to intermittently form a closed sheet feeding nip with said first and larger radius circumferential surface areas with said idlers, selectively intermittently further partially rotating said at least two sheet feeding and registration rollers to intermittently form an open non sheet feeding gap from said idlers with said second and smaller radius of said second circumferential surface areas, intermittently laterally shifting said at least two spaced apart sheet feeding rollers laterally relative to said sheet path direction while a sheet is engaged in said closed sheet feeding nip of said at least two sheet feeding rollers for laterally registering the sheet, and intermittently laterally shifting said at least two spaced apart sheet feeding rollers towards said home position thereof without laterally moving a sheet while a sheet is in said intermittent sheet disengaged nips of said at least two sheet feeding rollers to provide increased time for said laterally shifting of said at least two sheet feeding rollers towards said home position, and/or wherein said opposing idlers laterally move together with said at least two spaced apart sheet feeding rollers, and said two spaced apart sheet feeding rollers have similar major larger radius cylindrical circumferential lengths and minor smaller radius non-cylindrical circumferential lengths respectively automatically providing with said rotation thereof closed nip sheet feeding and open nip sheet release relative to said opposing idlers, and/or wherein said larger radius circumferential lengths of said at least two spaced apart sheet feeding rollers are greater than the downstream distance to a subsequent sheet acquisition system, and/or a high speed printer with an image transfer station in said sheet path, having a sheet acquisition system downstream in said sheet path comprising non-slip sheet feeding nips positioned in said sheet path between said sheet lateral registration method and said image transfer station of said high speed printer, wherein said at least two spaced apart sheet feeding rollers provide sheet deskewing by differential rotation as well as said lateral sheet registration, and/or wherein said at least two spaced apart sheet feeding rollers are integral a high speed printer sheet path having closely sequentially spaced print media sheets moving at high speed therein, and said at least two spaced apart sheet feeding rollers provide both lateral registration and deskewing of said closely sequentially spaced print media sheets.
The disclosed system may be operated and controlled by appropriate operation of conventional control systems. It is well known and preferable to program and execute imaging, printing, paper handling, and other control functions and logic with software instructions for conventional or general purpose microprocessors, as taught by numerous prior patents and commercial products. Such programming or software may of course vary depending on the particular functions, software type, and microprocessor or other computer system utilized, but will be available to, or readily programmable without undue experimentation from, functional descriptions, such as those provided herein, and/or prior knowledge of functions which are conventional, together with general knowledge in the software or computer arts. Alternatively, the disclosed control system or method may be implemented partially or fully in hardware, using standard logic circuits or single chip VLSI designs.
The term xe2x80x9creproduction apparatusxe2x80x9d or xe2x80x9cprinterxe2x80x9d as used herein broadly encompasses various printers, copiers or multifunction machines or systems, xerographic or otherwise, unless otherwise defined in a claim. The term xe2x80x9csheetxe2x80x9d herein refers to a usually flimsy physical sheet of paper, plastic, or other suitable physical substrate for images, whether precut or web fed. A xe2x80x9ccopy sheetxe2x80x9d may be abbreviated as a xe2x80x9ccopyxe2x80x9d or called a xe2x80x9chardcopy.xe2x80x9d
As to specific components of the subject apparatus or methods, or alternatives therefor, it will be appreciated that, as is normally the case, some such components are known per se in other apparatus or applications which may be additionally or alternatively used herein, including those from art cited herein. All references cited in this specification, and their references, are incorporated by reference herein where appropriate for teachings of additional or alternative details, features, and/or technical background. What is well known to those skilled in the art need not be described herein.